O/A works very well *especially* in the small sizes being discussed.
The key is to use a small enough torch and keep the flame constantly
in motion. Propane is OK for larger jobs, but a Lil' Torch affords
the pinpoint control required for silverbrazing small stuff close
together. That's why jewellers use them.

Forgive the pitch, but I happen to have a "Little Torch" outfit for sale,
that I just haven't gotten around to posting on eBay. It is their 23-2003
kit set up for O/A, including the hoses and regulators for the small "MC"
acetylene cylinder. Mine includes only three or four of the standard tips,
but also a twin flame tip, which allows for very quick heating of the joint
by surrounding it with flame from two directions. (see
http://www.littletorch.com/tips.html)

I am asking $195 plus shipping from Austin, TX, and I will throw in the rest
of the roll of silver solder and flux that I purchased to braze stainless
rod. (I ended up with a TIG welder more suited for my purposes.)

email me if interested - emmo at austin.rr.com